The present invention relates to a liquid transfer method and liquid transfer apparatus which transfer a liquid such as varnish or ink to the two surfaces of a sheet.
As a conventional liquid transfer apparatus, one disclosed in Japanese Patent Laid-Open No. 2003-182031 is available. This liquid transfer apparatus comprises a first blanket cylinder (transport cylinder) which holds and conveys a sheet by gripping its one edge, and a second blanket cylinder which opposes the first blanket cylinder. As the sheet passes between the first and second blanket cylinders, varnish is transferred from the second blanket cylinder to the obverse of the sheet, thus coating the obverse of the sheet. Simultaneously, the printing pressure of the second blanket cylinder transfers the varnish from the first blanket cylinder to the reverse of the sheet, thus coating the reverse of the sheet as well.
In the conventional apparatus described above which transfers the liquid to the sheet, when performing overall coating on the two surfaces of the sheet, the following problem occurs. Note that overall coating refers to coating of the sheet entirely excluding margins reserved on the leading, trailing, left, and right edges of the sheet. When overall coating is to be performed on a sheet printed with ink, overall coating refers to coating that completely covers the images and register marks printed with the ink.
When performing overall coating on the two surfaces of the sheet, immediately after the leading edge of the sheet passes between the first and second blanket cylinders, the leading edge of the obverse of the sheet undesirably adheres to the second blanket cylinder due to the tackiness of the varnish on the obverse of the sheet, so that the leading edge of the reverse of the sheet is sometimes pulled to be separate from the surface of the first blanket cylinder. Then, transfer nonuniformities occur in the varnish transferred from the first blanket cylinder to the reverse of the sheet to degrade the coating quality. This problem also arises in a printing apparatus which prints using high-viscosity ink.